Storage library systems are capable of storing and rapidly retrieving large quantities of information stored on storage media cartridges. Such storage library systems often use robotic mechanisms to improve the speed of information retrieval and the reliability of maintaining the storage library cartridge inventory. These robotic mechanisms typically include a hand mechanism positioned on a robotically movable arm. To retrieve information, the robotic arm is moved to position the hand near the inventory location of a desired media cartridge. The hand may include a camera or robotic eye to read the volume serial numbers (VOLSERs) of the cartridges to search for the desired cartridge.
Upon locating the desired cartridge, the hand is activated to grip and remove it from the library inventory location. The robotic arm then moves to an appropriate position to further process the cartridge. For instance, the robotic arm may insert the cartridge into an appropriate tape drive and then remove the cartridge from the drive at the appropriate time and return the cartridge to the appropriate library inventory location. In this manner, the robotic hand manipulates the cartridge for access to information stored on the cartridge.
Generally, the storage library system includes a plurality of stacks of cartridges which are accessible by means of the above-described robotic handling mechanism. Typically, the cartridges are stored within magazines having a plurality of cells formed therein for receiving the cartridges. The magazines are supported by a receiver such that the cartridges are exposed for retrieval by the robotic handling mechanism.
It is sometimes desirable to remove and install magazines as modular units in the storage library system for providing access to different types of information in groups. Accordingly, such magazines may be periodically removed from the storage library system while containing cartridges within the cells of the magazine. Accordingly, it is desirable to have the cartridges normally locked within the magazine when the magazine is outside of the storage library system for handling, and further to have the cartridges automatically unlocked for removal from the cells as the magazine is inserted into the respective receiver.
U.S. Pat. No. 5,795,042, disclosed by the present applicant and hereby incorporated by reference, discloses a storage library system in which the cartridge cells are normally locked when the magazine is outside of the receiver and automatically unlocked as the magazine is inserted into the receiver. A problem with typical storage library system magazines such as the magazine disclosed in U.S. Pat. No. 5,795,042 is that the cartridges stored in the cells are not held steady and may be positioned inaccurately within the cells when the cells are either locked or unlocked. Consequently, the cartridges stored in the cells may be subject to vibration as the magazine is moved when the magazine is outside of the receiver even though the cells are locked. When the magazine is inside the receiver and the cells are unlocked, the cartridges can move slightly when gripped by the robotic hand making it more difficult or impossible for the hand to remove the cartridges. The cartridges may also not be positioned accurately within the cells thereby possibly causing the camera of the robotic hand to misread the VOLSERs of the cartridges.
Variations in the storage position of the cartridges can cause catastrophic malfunctions in the robotic arm. An arm attempting to insert a miscentered cartridge into a tape drive may catch an edge of the cartridge on an edge of the drive. The torsion encountered when the arm attempts to push the cartridge into the drive can twist the cartridge sideways or even cause the cartridge to drop from the arm. In other circumstances, the arm may not be able to grasp the cartridge or may only be able to obtain a precarious grasp that presents a risk of dropping the cartridge.